Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965248AbbFJSTO (ORCPT ); Wed, 10 Jun 2015 14:19:14 -0400 Received: from mail-la0-f46.google.com ([209.85.215.46]:34733 "EHLO mail-la0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752492AbbFJSTD (ORCPT ); Wed, 10 Jun 2015 14:19:03 -0400 MIME-Version: 1.0 In-Reply-To: <20150610181650.GA11579@suse.com> References: <20150610181650.GA11579@suse.com> From: Andy Lutomirski Date: Wed, 10 Jun 2015 11:18:40 -0700 Message-ID: Subject: Re: [PATCH v5 02/10] x86: Compile-time asm code validation To: Vojtech Pavlik Cc: Josh Poimboeuf , Michal Marek , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "linux-kernel@vger.kernel.org" , Andi Kleen , live-patching@vger.kernel.org, X86 ML , "H. Peter Anvin" , Linus Torvalds , Peter Zijlstra Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1521 Lines: 34 On Wed, Jun 10, 2015 at 11:16 AM, Vojtech Pavlik wrote: > On Wed, Jun 10, 2015 at 10:21:36AM -0700, Andy Lutomirski wrote: >> On Jun 10, 2015 5:07 AM, "Josh Poimboeuf" wrote: >> > >> > Add a new CONFIG_ASM_VALIDATION option which adds an asmvalidate host >> > tool which runs on every compiled .S file. Its goal is to enforce sane >> > rules on all asm code, so that stack debug metadata (frame/back chain >> > pointers and/or DWARF CFI metadata) can be made reliable. >> > >> > It enforces the following rules: >> > >> > 1. Each callable function must be annotated with the ELF STT_FUNC type. >> > This is typically done using the ENTRY/ENDPROC macros. If >> > asmvalidate finds a return instruction outside of a function, it >> > flags an error, since that usually indicates callable code which >> > should be annotated accordingly. >> > >> > 2. Each callable function must never leave its own bounds (i.e. with a >> > jump to outside the function) except when returning. >> >> Won't that break with sibling/tail calls? GCC can generate those, and >> the ia32_ptregs_common label is an example of such a thing. > > It only validates hand-written assembly, so how it could? > It's a hand-written tail call. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/